1. Field of the Invention
The present invention relates to a pressure switch that measures the pressure of a fluid.
2. Description of the Related Art
Heretofore, as a means for ensuring that various types of machines can safely be driven automatically, pressure switches have widely been used. By setting beforehand a pressure threshold on the side of a pressure switch that is connected to various devices, excessive fluid pressures generated at a location where the pressure switch is disposed are detected mechanically and/or electrically, whereupon a detection signal can be issued immediately to notify the various devices.
For example, in the case that an air filter, a regulator, a lubricator, or the like, which make up types of air pressure auxiliary devices, are interconnected mutually via metal fittings, it is often the case that pressure switches are installed on such metal fittings. In this type of situation, a pressure switch that is small in size and lightweight preferably should be used.
In Japanese Laid-Open Patent Publication No. 10-208597, a technical concept is disclosed concerning a pressure switch, which comprises an adjustment screw for setting a pressure threshold value, a swivel plate screw-engaged with the adjustment screw and which slides under a linkage with rotary movement of the adjustment screw, a movable needle formed integrally with the swivel plate, and a display window, which is disposed on a part of a casing. In greater detail, in the vicinity of both sides of the display window provided on the casing, scale markings and a row of Arabic numbers are provided, together with a pointer consisting of a line colored in red or the like on an upper surface of the movable needle, which is applied by printing or the like.
As a result of being constructed in this manner, and by displaying in combination the needle, the scale markings and the row of Arabic numbers, the preset pressure threshold can be confirmed visually from an external area outside of the casing. Accordingly, while reading the numerical values of the scale markings pointed to and indicated by the needle, an operator turns the adjustment screw, whereby the threshold value of the pressure switch can easily be set. Naturally, when measurements are performed, measured pressures are capable of being confirmed visually as well by the numerical values of the scale markings which are indicated by the pointer.
However, in the pressure switch disclosed in Japanese Laid-Open Patent Publication No. 10-208597, since it is necessary that the plane in which the display window is formed be parallel to the displacement direction of the swivel plate, the planes in which the display window and the swivel plate are formed must be mutually perpendicular to each other.
Notwithstanding, in the case that the swivel plate in the aforementioned pressure switch is constructed from a metal plate, in order to form a separate movable needle, an L-shaped bending process must be carried out. Further, in order to display the pointer, which is made up of a red line or the like on the movable needle, it is necessary to perform a process step of engraving with respect to the metal plate, and a separate process step of applying color thereto.
In this manner, in the case that a pointer is to be provided on the movable needle after the swivel plate and the movable needle have been formed integrally using a metal plate, separate processing steps, together with an increase in the number of parts, are required. Consequently, a disadvantage results in that manufacturing costs for the pressure switch are increased.